// variant.hpp - v1.0
/*
 *  Copyright (c) 2007 Leigh Johnston.
 *
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 *     * Neither the name of Leigh Johnston nor the names of any
 *       other contributors to this software may be used to endorse or
 *       promote products derived from this software without specific prior
 *       written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 *  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 *  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#pragma once

#include "neolib.hpp"

#include <type_traits>
#include <variant>

namespace neolib
{
    typedef std::monostate none_t;
    const none_t none;

    template <typename... Types>
    class variant : public std::variant<none_t, Types...>
    {
    public:
        typedef std::variant<none_t, Types...> value_type;
    public:
        variant() :
            value_type()
        {
        }
        variant(const variant& aOther) :
            value_type{ static_cast<const value_type&>(aOther) }
        {
        }
        variant(variant&& aOther) :
            value_type{ static_cast<value_type&&>(std::move(aOther)) }
        {
        }
        template <typename T, std::enable_if_t<!std::is_same_v<std::decay_t<T>, variant>, int> = 0>
        variant(T&& aArgument) : 
            value_type{ std::forward<T>(aArgument) }
        {
        }
    public:
        variant& operator=(const variant& aOther)
        {
            value_type::operator=(static_cast<const value_type&>(aOther));
            return *this;
        }
        variant& operator=(variant&& aOther)
        {
            value_type::operator=(static_cast<value_type&&>(std::move(aOther)));
            return *this;
        }
        template <typename T, std::enable_if_t<!std::is_same_v<std::decay_t<T>, variant>, int> = 0>
        variant& operator=(T&& aArgument)
        {
            value_type::operator=(std::forward<T>(aArgument));
            return *this;
        }
    public:
        const value_type& for_visitor() const
        {
            return *this;
        }
        value_type& for_visitor()
        {
            return *this;
        }
    public:
        bool operator==(const none_t) const
        {
            return std::holds_alternative<std::monostate>(*this);
        }
        bool operator!=(const none_t) const
        {
            return !std::holds_alternative<std::monostate>(*this);
        }
    };

    // Deprecated, use std::get.
    template <typename T, typename Variant>
    inline T static_variant_cast(const Variant& aVariant)
    {
        typedef T result_type;
        typedef typename std::remove_cv<typename std::remove_reference<result_type>::type>::type alternative_type;
        auto& result = std::get<alternative_type>(aVariant);
        return static_cast<result_type>(result);
    }

    // Deprecated, use std::get.
    template <typename T, typename Variant>
    inline T static_variant_cast(Variant& aVariant)
    { 
        typedef T result_type;
        typedef typename std::remove_cv<typename std::remove_reference<result_type>::type>::type alternative_type;
        auto& result = std::get<alternative_type>(aVariant);
        return static_cast<result_type>(result);
    }
}

namespace std
{
    template <typename Visitor, typename... Types>
    auto visit(Visitor&& vis, const neolib::variant<Types...>& var)
    {
        return std::visit(std::forward<Visitor>(vis), var.for_visitor());
    }

    template <typename Visitor, typename... Types>
    auto visit(Visitor&& vis, neolib::variant<Types...>& var)
    {
        return std::visit(std::forward<Visitor>(vis), var.for_visitor());
    }
}

// Deprecated, use std::get.
using neolib::static_variant_cast;